Resin tube

Abstract

To provide a resin tube that contains poly (3-hydroxyalkanoate)-based resin component, and has improved impact resistance at a low temperature.SOLUTION: A resin tube contains a copolymer (A) consisting of 3-hydroxybutyrate unit which has a poly(3-hydroxyalkanoate)-based resin component having the weight-average molecular weight of 400,000 or more and less than 700,000 and the content ratio of 3-hydroxybutyrate unit by 50 mol% or more and 76 mol% or less, and another hydroxyalkanoate unit, and a copolymer (B) consisting of 3-hydroxybutyrate unit having the weight-average molecular weight of 700,000 or more and another hydroxyalkanoate unit, where the content of the copolymer (A) out of the total amount of the poly(3-hydroxyalkanoate)-based resin component is 21 wt.% or more and 40 wt.% or less, and the content of the copolymer (B) is 1 wt.% or more and 20 wt.% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin tube containing a poly(3-hydroxyalkanoate) resin. [Background technology]

[0002] In recent years, the separate collection and composting of food waste has been promoted, particularly in Europe, and there is a demand for plastic products that can be composted together with food waste. Furthermore, with marine pollution caused by microplastics coming to the forefront, there is hope for the development of plastics that can be decomposed in seawater.

[0003] Poly(3-hydroxyalkanoate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species. They are also biodegradable not only in soil but also in seawater, and are therefore attracting attention as a material that can solve the above problems.

[0004] The use of such poly(3-hydroxyalkanoate) resins as resin materials for forming resin tubes such as straws is being investigated.

[0005] Patent Documents 1 and 2 disclose resin tubes containing at least two types of poly(3-hydroxyalkanoate) resins that differ from each other in the type of constituent monomer and / or the content ratio of the constituent monomer.

[0006] Patent Document 3 also discloses that by using a poly(3-hydroxyalkanoate) resin having a weight-average molecular weight of 300,000 to 500,000 and in which the proportion of components having a weight-average molecular weight of 250,000 or less in the molecular weight distribution is 15 to 40% by weight, a resin tube that is high in strength and can be molded at high speed can be provided. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2022 / 009717 [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-8387 [Patent Document 3] International Publication No. 2023 / 100673 Summary of the Invention [Problem to be solved by the invention]

[0008] Resin tubes are required to be resistant to cracking during production, transportation, and use, i.e., to have impact resistance. In particular, when resin tubes are stored in a refrigerator, they are required to have good impact resistance even at low temperatures.

[0009] However, it is not easy to obtain a resin tube with good impact resistance at low temperatures using the poly(3-hydroxyalkanoate) resin compositions disclosed in Patent Documents 1 to 3. Furthermore, Patent Document 1 describes that a resin tube with excellent impact resistance can be provided, but does not describe impact resistance at low temperatures.

[0010] In view of the above-mentioned current situation, an object of the present invention is to provide a resin tube which contains a poly(3-hydroxyalkanoate)-based resin component and has improved impact resistance at low temperatures. [Means for solving the problem]

[0011] As a result of intensive research to solve the above-mentioned problems, the inventors have discovered that a resin tube with improved impact resistance at low temperatures can be provided by using, in specific proportions, a copolymer having a relatively low weight-average molecular weight and a relatively low content of 3-hydroxybutyrate units, and a copolymer having a relatively high weight-average molecular weight, as a poly(3-hydroxyalkanoate)-based resin, and have thus completed the present invention.

[0012] That is, the present invention provides a resin tube containing a poly(3-hydroxyalkanoate)-based resin component, The poly(3-hydroxyalkanoate) resin component is A copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units, having a weight average molecular weight of 400,000 or more and less than 700,000 and a content of 3-hydroxybutyrate units of 50 mol% or more and 76 mol% or less, and The copolymer (B) contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, and has a weight-average molecular weight of 700,000 or more. The present invention relates to a resin tube in which the content of copolymer (A) is 21% by weight or more and 40% by weight or less, and the content of copolymer (B) is 1% by weight or more and 20% by weight or less, based on the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a resin tube which contains a poly(3-hydroxyalkanoate)-based resin component and has improved impact resistance at low temperatures. According to the present invention, it is possible to provide a resin tube containing a poly(3-hydroxyalkanoate) resin that is resistant to cracking even in a low-temperature environment. A resin tube according to a preferred embodiment of the present invention has a good elastic modulus at room temperature and / or good elongation at low temperatures. Furthermore, the resin tube according to the present invention has good solidification properties after melting, and therefore can be produced at a high molding speed, thereby providing a resin tube with improved impact resistance at low temperatures and high productivity. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. One embodiment of the present invention relates to a resin tube containing a poly(3-hydroxyalkanoate)-based resin component.

[0015] (Poly(3-hydroxyalkanoate) resin) The poly(3-hydroxyalkanoate) resin is a polymer having a 3-hydroxyalkanoate unit, and specifically, is preferably a polymer containing a unit represented by the following general formula (1). [-CHR-CH2-CO-O-] (1) In the general formula (1), R is C p H 2p+1 where p is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. p is preferably 1 to 10, and more preferably 1 to 8.

[0016] The poly(3-hydroxyalkanoate) resin is preferably a poly(3-hydroxyalkanoate) resin produced by a microorganism, in which all 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0017] The poly(3-hydroxyalkanoate) resin preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more of the total structural units. The poly(3-hydroxyalkanoate) resin may contain only 3-hydroxyalkanoate units as structural units of the polymer, or may contain one or more types of 3-hydroxyalkanoate units as well as other units (e.g., 4-hydroxyalkanoate units).

[0018] The poly(3-hydroxyalkanoate) resin may be a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units. In particular, it is preferred that all 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units. It is also preferred that the poly(3-hydroxyalkanoate) resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0019] Specific examples of poly(3-hydroxyalkanoate) resins include poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH). Examples of suitable polyhydroxybutyrates include poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB). In particular, from the viewpoints of productivity and mechanical properties of molded articles, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0020] When the poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units, the average content of 3-hydroxybutyrate units in the total monomer units (i.e., the total of 3-hydroxybutyrate units and other hydroxyalkanoate units) in the entire poly(3-hydroxyalkanoate) resin component contained in the resin tube of the present disclosure is preferably 65 to 98 mol%, more preferably 75 to 96 mol%, even more preferably 80 to 95 mol%, and particularly preferably 85 to 96 mol%, from the viewpoint of achieving both the mechanical properties and productivity of the resin tube.

[0021] The average content of 3-hydroxybutyrate units in the total number of monomer units in the entire poly(3-hydroxyalkanoate) resin component can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of WO 2013 / 147139. The content of 3-hydroxybutyrate units in each copolymer or resin described below can also be determined in a similar manner.

[0022] The weight average molecular weight measured for the entire poly(3-hydroxyalkanoate) resin component contained in the resin tube of the present disclosure is preferably 100,000 to 1,500,000, more preferably 200,000 to 1,000,000, and particularly preferably 300,000 to 800,000, from the viewpoint of achieving both mechanical properties and productivity of the resin tube.

[0023] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin component can be measured in terms of polystyrene using gel permeation chromatography (HPLC GPC system manufactured by Shimadzu Corporation) using a chloroform solution. A column suitable for measuring weight-average molecular weights can be used as the column for gel permeation chromatography. The weight-average molecular weights of the copolymers or resins described below can also be determined in the same manner.

[0024] The poly(3-hydroxyalkanoate) resin component contained in the resin tube according to the present disclosure is preferably not cross-linked using a cross-linking agent such as an organic peroxide, i.e., it is preferable that it does not have a cross-linked structure.

[0025] The resin tube according to the present disclosure contains, as the poly(3-hydroxyalkanoate) resin component, at least two types of poly(3-hydroxyalkanoate) resins having different weight-average molecular weights.

[0026] Specifically, the poly(3-hydroxyalkanoate) resin component contained in the resin tube according to the present disclosure contains at least the following two types of resins. A copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units, having a weight average molecular weight of 400,000 or more and less than 700,000 and a content of 3-hydroxybutyrate units of 50 mol% or more and 76 mol% or less, and Copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units having a weight-average molecular weight of 700,000 or more

[0027] As described above, by using a poly(3-hydroxyalkanoate) copolymer (A) having a relatively low weight-average molecular weight and a relatively low content of 3-hydroxybutyrate units in combination with a 3-hydroxybutyrate unit-containing copolymer (B) having a relatively high weight-average molecular weight, a synergistic effect can be achieved to improve the impact resistance of the resin tube at low temperatures.

[0028] Copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units is a low-crystalline poly(3-hydroxyalkanoate) resin because it contains a relatively low proportion of 3-hydroxybutyrate units. Low-crystalline poly(3-hydroxyalkanoate) resins have good toughness. Therefore, by using copolymer (A), the impact resistance of resin tubes at low temperatures can be improved.

[0029] In the copolymer (A), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is 50 mol% or more and 76 mol% or less. From the viewpoint of the impact resistance of the resin tube, the upper limit of this percentage is preferably 74 mol% or less, more preferably 72 mol% or less. Furthermore, from the viewpoint of the productivity of the copolymer (A), the lower limit of this percentage is preferably 60 mol% or more, more preferably 70 mol% or more.

[0030] As the copolymer (A), at least two types of copolymers having different types of constituent monomers and / or different content ratios of the constituent monomers may be used in combination. When the copolymer (A) contains multiple types of resins, the content ratio of 3-hydroxybutyrate units in each of the multiple types of resins may be within the above-mentioned range.

[0031] As the copolymer (A), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0032] The weight-average molecular weight of copolymer (A) is in the range of 400,000 or more and less than 700,000. A relatively low weight-average molecular weight of copolymer (A) ensures fluidity during melt processing, enabling resin tubes to be produced with good productivity. From the viewpoint of resin tube productivity, the molecular weight is preferably 650,000 or less. While there are no particular restrictions on the lower limit, from the viewpoint of the impact resistance of the resin tube, it is preferably 200,000 or more, more preferably 300,000 or more, even more preferably 400,000 or more, and particularly preferably 500,000 or more.

[0033] As the copolymer (A), at least two types of copolymers having different weight-average molecular weights may be used in combination. When the copolymer (A) contains multiple types of resins, it is sufficient that the weight-average molecular weight of each of the multiple types of resins falls within the above-mentioned range.

[0034] On the other hand, copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units has a weight-average molecular weight of 700,000 or more. By using such a copolymer with a relatively high molecular weight in combination with copolymer (A), the impact resistance of the resin tube at low temperatures can be improved. Furthermore, by using high-molecular-weight copolymer (B) in combination with copolymer (A), the solidification property of the poly(3-hydroxyalkanoate) resin component is improved, and the molding speed of the resin tube can be increased.

[0035] The weight average molecular weight of the copolymer (B) is preferably 750,000 or more. Although there is no particular upper limit, from the viewpoint of productivity, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less.

[0036] As the copolymer (B), at least two types of copolymers having different weight-average molecular weights may be used in combination. When the copolymer (B) contains multiple types of resins, it is sufficient that the weight-average molecular weight of each of the multiple types of resins falls within the above-mentioned range.

[0037] The difference in weight-average molecular weight between copolymer (A) and copolymer (B) is not particularly limited, but is preferably 50,000 or more, more preferably 100,000 or more, so that the respective effects of (A) and (B) can be more easily exhibited.

[0038] In copolymer (B), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is preferably 50 mol% or more and 92 mol% or less, since this facilitates the achievement of the effect of improving the impact resistance of the resin tube by incorporating copolymer (B). It is more preferably 60 to 91 mol%, even more preferably 70 to 90 mol%, and particularly preferably 80 to 89 mol%. This content may be 76 mol% or less, or may be more than 76 mol%.

[0039] As the copolymer (B), at least two types of copolymers having different types of constituent monomers and / or different content ratios of the constituent monomers may be used in combination. When the copolymer (B) contains multiple types of resins, the content ratio of 3-hydroxybutyrate units in each of the multiple types of resins may be within the above-mentioned range.

[0040] As the copolymer (B), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred.

[0041] In the resin tube according to the present disclosure, the content of copolymer (A) is set to be 21% by weight or more and 40% by weight or less, and the content of copolymer (B) is set to be 1% by weight or more and 20% by weight or less, based on the total amount of the poly(3-hydroxyalkanoate)-based resin components. By using both copolymers in this range, the impact resistance of the resin tube at low temperatures can be improved. If the amount of copolymer (A) is less than 21% by weight, or if the content of copolymer (B) is less than 1% by weight, it becomes difficult to obtain an effect of improving impact resistance at low temperatures.

[0042] On the other hand, if the amount of copolymer (A) exceeds 40% by weight, the elastic modulus of the resin tube decreases, and the poly(3-hydroxyalkanoate) resin component is less likely to crystallize and solidify, which tends to reduce the productivity of the resin tube. Also, if the content of copolymer (B) exceeds 20% by weight, the melt viscosity of the poly(3-hydroxyalkanoate) resin component increases, which tends to reduce the productivity of the resin tube.

[0043] The lower limit of the content of copolymer (A) is preferably 24% by weight or more, more preferably 26% by weight or more, from the viewpoint of improving the low-temperature elongation of the resin tube, and the upper limit of the content of copolymer (A) is preferably 35% by weight or less, more preferably 33% by weight or less, and even more preferably 31% by weight or less, from the viewpoint of improving the elastic modulus of the resin tube.

[0044] The upper limit of the content of copolymer (B) is preferably 15% by weight or less, more preferably 10% by weight or less, even more preferably 8% by weight or less, and particularly preferably 6% by weight or less. The lower limit of the content of copolymer (B) is preferably 2% by weight or more, more preferably 3% by weight or more, and even more preferably 4% by weight or more.

[0045] The resin tube according to the present disclosure may contain a poly(3-hydroxyalkanoate)-based resin (C) that does not conform to the definitions of copolymer (A) and copolymer (B). While the poly(3-hydroxyalkanoate)-based resin (C) can be selected as appropriate, from the viewpoints of productivity of the resin tube, impact resistance, low-temperature elongation, and elastic modulus of the resin tube, it is preferable to further contain at least poly(3-hydroxybutyrate) (C1) and / or a copolymer (C2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, which has a weight-average molecular weight of 100,000 or more but less than 700,000 and a 3-hydroxybutyrate unit content of 94 mol% or more but less than 99 mol%. While either (C1) or (C2) alone may be used, it is more preferable to include both (C1) and (C2).

[0046] Poly(3-hydroxybutyrate) (C1) and copolymer (C2) have a high content of 3-hydroxybutyrate units, making them highly crystalline poly(3-hydroxyalkanoate)-based resins. Highly crystalline poly(3-hydroxyalkanoate)-based resins have good strength. This makes it easier to maintain the elastic modulus of the resin tube within a favorable range. Furthermore, the use of (C1) can improve the productivity of resin tubes.

[0047] Poly(3-hydroxybutyrate) (C1) refers to a homopolymer of 3-hydroxybutyrate or a polymer containing, in addition to 3-hydroxybutyrate units, a small amount of hydroxyalkanoate units other than 3-hydroxybutyrate units. Specifically, the content of 3-hydroxybutyrate units in the total constituent monomers of poly(3-hydroxybutyrate) (C1) is preferably more than 99 mol % and 100 mol % or less.

[0048] The hydroxyalkanoate units other than 3-hydroxybutyrate units that can be contained in poly(3-hydroxybutyrate) (C1) are not particularly limited as long as they are copolymerizable with 3-hydroxybutyrate units, and examples thereof include 3-hydroxyalkanoate units other than 3-hydroxybutyrate units and hydroxyalkanoate units other than 3-hydroxyalkanoate units (e.g., 4-hydroxyalkanoate units). In particular, 3-hydroxyhexanoate units are preferred.

[0049] The weight-average molecular weight of poly(3-hydroxybutyrate) (C1) is not particularly limited, but is preferably in the range of 100,000 or more but less than 700,000 from the viewpoint of productivity and mechanical properties of the resin tube. The lower limit is more preferably 200,000 or more. The upper limit is preferably 600,000 or less, more preferably 500,000 or less, and particularly preferably 400,000 or more.

[0050] In the copolymer (C2), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is 94 mol% or more and 99 mol% or less. From the viewpoint of productivity and mechanical properties of the resin tube, the lower limit of this percentage is preferably 96 mol% or more. The upper limit of this percentage may be 98 mol% or less.

[0051] As the copolymer (C2), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0052] The copolymer (C2) may be a mixture of at least two copolymers differing in the type and / or content of the constituent monomers, provided that the content of the 3-hydroxybutyrate unit in each of the copolymers falls within the above-mentioned range.

[0053] The weight-average molecular weight of the copolymer (C2) is preferably in the range of 100,000 or more and less than 700,000 from the viewpoint of productivity and mechanical properties of the resin tube. The lower limit is more preferably 200,000 or more. The upper limit is preferably 600,000 or less, more preferably 500,000 or less, and particularly preferably 400,000 or more.

[0054] As the copolymer (C2), at least two types of copolymers having different weight-average molecular weights may be used in combination. When the copolymer (C2) contains multiple types of resins, it is sufficient that the weight-average molecular weight of each of the multiple types of resins falls within the above-mentioned range.

[0055] The total content of poly(3-hydroxybutyrate) (C1) and copolymer (C2) is preferably 40% by weight or more of the total amount of poly(3-hydroxyalkanoate)-based resin components contained in the resin tube according to the present disclosure. Using (C1) and / or (C2) in such an amount facilitates maintaining the elastic modulus of the resin tube within a favorable range and improves the productivity of the resin tube. The content is preferably 45% by weight or more, more preferably 50% by weight or less. The upper limit of the content is preferably 78% by weight or less, more preferably 70% by weight or less, and even more preferably 60% by weight or less.

[0056] The content of poly(3-hydroxybutyrate) (C1) is preferably 1% by weight or more and 20% by weight or less of the total amount of poly(3-hydroxyalkanoate)-based resin components contained in the resin tube according to the present disclosure. Using (C1) in such an amount improves the productivity of the resin tube and enables the production of a resin tube with a good appearance. The upper limit is preferably 18% by weight or less, more preferably 15% by weight or less. The lower limit is preferably 3% by weight or more, more preferably 5% by weight or more, even more preferably 8% by weight or more, and particularly preferably 10% by weight or more.

[0057] The resin tube according to the present disclosure may further contain, as the poly(3-hydroxyalkanoate)-based resin (C) that does not meet the definitions of copolymer (A) and copolymer (B), a copolymer (C3) of 3-hydroxybutyrate units and other hydroxyalkanoate units other than poly(3-hydroxybutyrate) (C1) and copolymer (C2).

[0058] In the copolymer (C3), the content of 3-hydroxybutyrate units in the total of 3-hydroxybutyrate units and other hydroxyalkanoate units is not particularly limited, but may be more than 76 mol% and less than 94 mol%. The lower limit of this content is preferably 80 mol% or more, more preferably 85 mol% or more. The upper limit is preferably 92 mol% or less, more preferably 90 mol% or less.

[0059] As the copolymer (C3), the copolymers described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0060] The copolymer (C3) may be a mixture of at least two copolymers differing in the type and / or content of the constituent monomers, provided that the content of the 3-hydroxybutyrate unit in each of the copolymers falls within the above-mentioned range.

[0061] The weight-average molecular weight of the copolymer (C3) is not particularly limited, but is preferably in the range of 100,000 or more but less than 700,000 from the viewpoint of productivity and mechanical properties of the resin tube. The lower limit is more preferably 200,000 or more. The upper limit is preferably 600,000 or less, more preferably 500,000 or less, and particularly preferably 400,000 or more.

[0062] As the copolymer (C3), at least two types of copolymers having different weight-average molecular weights may be used in combination. When the copolymer (C3) contains multiple types of resins, it is sufficient that the weight-average molecular weight of each of the multiple types of resins falls within the above-mentioned range.

[0063] The content of copolymer (C3) is not particularly limited, but is preferably 1% by weight or more and 30% by weight or less of the total amount of poly(3-hydroxyalkanoate)-based resin components contained in the resin tube according to the present disclosure. Using (C3) in such an amount can improve the productivity of the resin tube. The content may be 5% by weight or more, or 10% by weight or more. The upper limit of the content may be 25% by weight or less, 20% by weight or less, or 15% by weight or less.

[0064] The method for producing poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a production method using chemical synthesis or a production method using a microorganism. Among these, a production method using a microorganism is preferred. Known methods can be applied to the production method using a microorganism. For example, known bacteria that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, for P3HB3HH, to increase productivity of P3HB3HH, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) or the like, into which genes encoding P3HA synthases have been introduced, is preferred. Microbial cells obtained by culturing these microorganisms under appropriate conditions and allowing P3HB3HH to accumulate within the cells can be used. Alternatively, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may be used depending on the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0065] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a method of obtaining a blend by microbial production or a method of obtaining a blend by chemical synthesis. Alternatively, a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, or the like, or by dissolving two or more resins in a solvent, mixing, and drying the resins.

[0066] (other resins) The resin tube according to the present disclosure may contain other resins besides the poly(3-hydroxyalkanoate)-based resin component, provided that the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester-based resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0067] The content of the other resin is not particularly limited, but is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, even more preferably 10 parts by weight or less, and particularly preferably 5 parts by weight or less, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate) resin component. It may also be 1 part by weight or less. The lower limit of the content of the other resin is not particularly limited, and may be 0 parts by weight.

[0068] (Plasticizer (D)) The resin tube according to the present disclosure preferably contains a plasticizer (D) in addition to the poly(3-hydroxyalkanoate)-based resin component. By blending the plasticizer (D), the impact resistance of the resin tube at low temperatures can be improved.

[0069] The plasticizer (D) is not particularly limited, but from the viewpoint of compatibility with the poly(3-hydroxyalkanoate)-based resin component, it is preferable to use an ester compound having an ester bond in the molecule.

[0070] Examples of ester compounds that can be used as plasticizers include modified glycerin compounds, dibasic acid ester compounds, adipate compounds, polyether ester compounds, benzoate ester compounds, citrate ester compounds, isosorbide ester compounds, and polycaprolactone compounds. Among these, modified glycerin ester compounds, dibasic acid ester compounds, adipate ester compounds, polyether ester compounds, and isosorbide ester compounds are preferred. The ester compounds can be used alone or in combination of two or more. When two or more compounds are used in combination, the mixing ratio of the ester compounds can be appropriately adjusted.

[0071] As the modified glycerin compound, a glycerin ester compound is preferred. As the glycerin ester compound, any of glycerin monoesters, diesters, and triesters can be used, but glycerin triesters are preferred from the viewpoint of compatibility with poly(3-hydroxyalkanoate) resin components. Among glycerin triesters, glycerin diacetomonoesters are particularly preferred. Specific examples of glycerin diacetomonoesters include glycerin diacetomonolaurate, glycerin diacetomonooleate, glycerin diacetomonostearate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate. Examples of the modified glycerin compound include Riken Vitamin's "Rikemal" PL series and "BIOCIZER."

[0072] Specific examples of dibasic acid ester compounds include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl) azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, diethyl succinate, and mixed-group dibasic acid ester compounds.

[0073] Examples of the adipate compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0074] Examples of polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0075] As the ester compound, a modified glycerin-based compound is preferred from the viewpoints of cost, versatility, and high biomass content. In particular, from the viewpoint of food contact, a glycerin triester is more preferred, a glycerin diacetomonoester is even more preferred, and glycerin diacetomonolaurate is particularly preferred.

[0076] The content of plasticizer (D) in the resin tube according to the present disclosure may be appropriately set taking into consideration the moldability, impact resistance, elongation, and modulus of elasticity of the resin tube, but is preferably 0 to 10 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. From the viewpoint of improving impact resistance, the lower limit of the content may be 0.1 parts by weight or more, preferably 0.5 parts by weight or more, preferably 1 part by weight or more, and more preferably 2 parts by weight or more. Furthermore, from the viewpoint of maintaining the modulus of elasticity within a good range, the upper limit of the content is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 2 parts by weight or less.

[0077] (additives) The resin tube according to the present disclosure may contain additives to the extent that the effects of the invention are not impaired. Examples of additives that can be used depending on the purpose include crystallization nucleating agents, lubricants, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, UV absorbers, colorants, inorganic fillers, organic fillers, and hydrolysis inhibitors. Biodegradable additives are particularly preferred.

[0078] Examples of crystallization nucleating agents include sugar alcohols such as pentaerythritol, galactitol, and mannitol; talc; fatty acid amides; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, because they are particularly effective in promoting the crystallization of the poly(3-hydroxyalkanoate) resin component. One or more crystallization nucleating agents may be used, and the ratio of their use can be appropriately adjusted depending on the purpose.

[0079] When a crystallization nucleating agent is used, its content is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate) resin component.

[0080] However, the resin tube according to the present disclosure may be substantially free of sugar alcohols such as pentaerythritol. "Substantially free of sugar alcohols" means that the sugar alcohol content is less than 0.1 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. It may also be less than 0.01 parts by weight. In an embodiment that is substantially free of sugar alcohols, it is possible to avoid the problems of bleed-out of sugar alcohols and the resulting contamination of the manufacturing equipment.

[0081] When sugar alcohols are not substantially blended, it is preferable to blend talc and / or a fatty acid amide as a crystallization nucleating agent. By using these crystallization nucleating agents, productivity of the resin tube can be improved even when sugar alcohols are not substantially blended. Specific examples of fatty acid amides are as follows: The fatty acid amides blended in the resin tube according to the present disclosure can function as both a crystallization nucleating agent and a lubricant.

[0082] Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauricamide, ethylenebiscapricamide, p-phenylenebisstearamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide and erucamide are preferred because of their particularly excellent lubricating effect on poly(3-hydroxyalkanoate)-based resin components. One or more types of lubricants may be used, and the ratio of their use can be adjusted appropriately depending on the purpose.

[0083] When a lubricant is used, its content is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, relative to 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. The resin tube according to the present disclosure preferably contains a lubricant, but does not necessarily need to contain one.

[0084] The resin tube according to the present disclosure may contain a filler. The inclusion of a filler can increase strength. The filler may be either an inorganic filler or an organic filler, or both may be used in combination. The inorganic filler is not particularly limited, but examples include talc, silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon black. Only one type of inorganic filler may be used, or two or more types may be used in combination.

[0085] When the filler is used, its content is not particularly limited, but is preferably 0.5 to 100 parts by weight, more preferably 1 to 80 parts by weight, even more preferably 3 to 70 parts by weight, and even more preferably 5 to 60 parts by weight, per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin components. However, the resin tube according to the present disclosure may be substantially free of a filler. "Substantially free of a filler" means that the content of the filler is less than 1 part by weight per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin components. It may also be less than 0.1 part by weight.

[0086] (Resin tube) In this specification, a tube refers to a hollow, elongated cylindrical molded product having a substantially uniform wall thickness and a substantially circular cross-sectional shape. The tube can be used as a straw or a pipe, but its uses are not limited to these.

[0087] When the resin tube according to the present disclosure is used as a straw, the thickness of the resin tube is preferably 0.01 mm or more and 0.6 mm or less, more preferably 0.05 mm or more and 0.5 mm or less, and even more preferably 0.1 mm or more and 0.4 mm or less, because the resin tube will not collapse when sucked when using it as a straw to drink a beverage, has appropriate flexibility so is less likely to break, is less likely to cause injury when poking a fingertip, and is rapidly biodegradable even in seawater.

[0088] Furthermore, when the resin tube according to the present disclosure is used as a straw, the outer diameter of the resin tube is not particularly limited, but is preferably 2 to 10 mm, more preferably 4 to 8 mm, and even more preferably 5 to 7 mm, for ease of use when using it as a straw to drink beverages.

[0089] When the resin tube according to the present disclosure is used as a pipe, the wall thickness of the resin tube can be appropriately set by a person skilled in the art, but is preferably 0.7 mm to 10 mm, more preferably 1 mm to 8 mm. The pipe can be suitably used in marine product farming and fishing.

[0090] The cross-sectional shape of the resin tube according to the present disclosure is generally circular, but from the viewpoint of usability as a straw or pipe, the closer to a perfect circle the better. Therefore, the flatness of the cross-sectional shape of the tube [100 × (maximum outer diameter − minimum outer diameter) / maximum outer diameter] is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and even more preferably 3% or less. A flatness of 0% means that the cross-sectional shape is a perfect circle.

[0091] The length of the resin tube according to the present disclosure is not particularly limited. However, when the resin tube is used as a straw, the length of the resin tube is preferably 50 to 350 mm, more preferably 70 to 300 mm, and even more preferably 90 to 270 mm, from the viewpoint of ease of use when using the resin tube as a straw to drink a beverage.

[0092] The resin tube used as a straw may be a tube that has not undergone secondary processing, or may be a tube that has undergone secondary processing such as the formation of a stopper portion or a bellows portion.

[0093] The resin tube according to the present disclosure preferably exhibits a 50% fracture energy measured at 2°C of 0.2 J or more and / or a 50% fracture energy measured at 5°C of 0.3 J or more. This allows the resin tube to exhibit good impact resistance at low temperatures and to be less susceptible to cracking during storage at low temperatures. The 50% fracture energy measured at 2°C is more preferably 0.3 J or more. The 50% fracture energy measured at 5°C is more preferably 0.4 J or more, and even more preferably 0.5 J or more. The upper limit of the 50% fracture energy at each temperature is not particularly limited, but may be, for example, 10 J or less, 5 J or less, 3 J or less, or 1 J or less.

[0094] A resin tube that satisfies the 50% fracture energy requirement can be realized by combining, as the poly(3-hydroxyalkanoate)-based resin component, a copolymer (A) that has a relatively low weight-average molecular weight and a relatively low content of 3-hydroxybutyrate units, and a copolymer (B) that has a relatively high weight-average molecular weight, in specific proportions, as described above. The wall thickness and diameter of the resin tube can be set so as to satisfy the 50% fracture energy requirement. The method for measuring the 50% breaking energy will be described in detail in the Examples section.

[0095] The resin tube according to the present disclosure can be produced by a known method, for example, by melting a blend of a poly(3-hydroxyalkanoate)-based resin component and other components in an extruder, extruding the blend through an annular die connected to the outlet of the extruder, and pouring it into water to solidify it into a tubular shape. Alternatively, the blend may be melt-extruded to form pellets, and the resulting pellets may be used to form a tube.

[0096] When the resin tube according to the present disclosure is subjected to secondary processing, the secondary processing may be performed at room temperature or under heating. The resin tube according to the present disclosure can be suitably subjected to secondary processing involving heating. The heating temperature during secondary processing can be appropriately set, and may be, for example, about 100 to 150°C.

[0097] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] A resin tube containing a poly(3-hydroxyalkanoate)-based resin component, The poly(3-hydroxyalkanoate) resin component is A copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units, having a weight average molecular weight of 400,000 or more and less than 700,000 and a content of 3-hydroxybutyrate units of 50 mol% or more and 76 mol% or less, and The copolymer (B) contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, and has a weight-average molecular weight of 700,000 or more. A resin tube, wherein the content of copolymer (A) is 21% by weight or more and 40% by weight or less, and the content of copolymer (B) is 1% by weight or more and 20% by weight or less, based on the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Item 2] Item 2. The resin tube according to item 1, wherein the copolymer (B) has a content of 3-hydroxybutyrate units of 50 mol % or more and 92 mol % or less. [Item 3] the poly(3-hydroxyalkanoate)-based resin component further comprises poly(3-hydroxybutyrate) (C1) and / or a copolymer (C2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, which has a weight-average molecular weight of 100,000 or more and less than 700,000 and a content of 3-hydroxybutyrate units of 94 mol% or more and 99 mol% or less, 3. The resin tube according to item 1 or 2, wherein the total content of the poly(3-hydroxybutyrate) (C1) and the copolymer (C2) is 40% by weight or more of the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Item 4] 4. The resin tube according to item 3, wherein the content of poly(3-hydroxybutyrate) (C1) is 10% by weight or more of the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Item 5] 5. The resin tube according to any one of items 1 to 4, wherein the content of the plasticizer (D) is 0 to 3 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component. [Item 6] 6. The resin tube according to any one of items 1 to 5, having a wall thickness of 0.01 mm or more and 10 mm or less. [Example]

[0098] The present invention will be specifically explained below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0099] The substances used in the examples and comparative examples are shown below. [Poly(3-hydroxyalkanoate) resin] Copolymer (A): P3HB3HH-30: P3HB3HH (average content ratio of 3HB / 3HH = 70.5 / 29.5 (mol% / mol%), weight average molecular weight is 640,000 g / mol) Produced in accordance with the method described in Example 9 of WO 2019 / 142845.

[0100] Copolymer (B): P3HB3HH-11H: P3HB3HH (Kaneka Biodegradable Polymer PHBH (registered trademark)) (average content ratio 3HB / 3HH = 89.0 / 11.0 (mol % / mol %), weight average molecular weight 750,000 g / mol) It was produced according to the method described in WO 2008 / 010296.

[0101] Poly(3-hydroxybutyrate) (C1): PHB: Poly(3-hydroxybutyrate) (weight average molecular weight: 300,000 g / mol) It was produced according to the method described in Comparative Example 1 of WO 2004 / 041936.

[0102] Copolymer (C2): P3HB3HH-3: P3HB3HH (average content ratio of 3HB / 3HH = 97.1 / 2.9 (mol% / mol%), weight average molecular weight is 300,000 g / mol) It was produced in accordance with the method described in Example 2 of WO 2019 / 142845. P3HB3HH-6: P3HB3HH (average content ratio of 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 500,000 g / mol) It was produced according to the method described in WO 2008 / 010296.

[0103] Copolymer (C3): P3HB3HH-13: P3HB3HH (Kaneka Biodegradable Polymer PHBH (registered trademark)) (average content ratio 3HB / 3HH = 87.1 / 12.9 (mol % / mol %), weight average molecular weight 330,000 g / mol)

[0104] [Additives] Additive-1: Behenamide (Nippon Fine Chemical Co., Ltd.: BNT-22H) Additive-2: Erucic acid amide (Neutron-S, manufactured by Nippon Fine Chemical Co., Ltd.)

[0105] [Plasticizer] Plasticizer: Glycerin diacetomonolaurate (Riken Vitamin Co., Ltd.: BIOCIZER)

[0106] The evaluation methods used in the examples and comparative examples are described below. [Measurement of impact resistance of tube molding] Tubes with an inner diameter of 5.6 mm, a thickness of 0.2 mm, and a length of 40 mm were prepared using the resin compositions described in the Examples and Comparative Examples. The tubes were cured for two hours in a thermostatic chamber set to the temperatures listed in Table 1. After curing, the tubes were quickly removed from the thermostatic chamber and placed on a 2 mm-thick rubber sheet with their axes horizontal. A 300 g rectangular weight was allowed to fall freely onto the tube from an arbitrary height above the top of the tube. The weight was dropped so that it contacted the entire tube. Based on the fracture results, the fracture height with a 50% probability was estimated, and the potential energy of the weight before the weight was dropped was calculated as the 50% fracture energy.

[0107] [Evaluation of tensile modulus] The produced tube molded article was cut into a No. 7 dumbbell shape conforming to JIS K 6251 to obtain a test piece. A tensile test was carried out in the MD direction of the tube in accordance with JIS K 7127 using a tensile tester (Shimadzu Corporation: EZ-LX 1kN) at a temperature of 23°C and a tension speed of 100 mm / min. The tensile modulus was calculated based on the SS curve obtained from the tensile test.

[0108] [Evaluation of tensile breaking strain at 0℃] The produced tube molded article was cut into a No. 7 dumbbell shape conforming to JIS K 6251 to obtain a test piece. A tensile test was carried out conforming to JIS K 7127 using a tensile tester (Shimadzu Corporation: AG-X 500N) in a thermostatic chamber set at 0°C at a tension rate of 1 mm / min. The tensile breaking strain was calculated based on the SS curve obtained from the tensile test.

[0109] Example 1 To obtain the resin composition shown in Table 1, 0.494 kg of P3HB3HH-30, 0.094 kg of P3HB3HH-11H, 0.248 kg of PHB, 0.87 kg of P3HB3HH-3, and 0.292 kg of P3HB3HH-13 were blended, and then 20 g of additive-1 and 10 g of additive-2 were added and blended. To produce resin composition pellets, melt extrusion was carried out using a φ26 mm co-rotating twin-screw extruder. The cylinder temperature and die temperature were both set to 150°C, and the obtained resin material (resin mixture) was charged and extruded. The extruded strand-like resin material was passed through a water tank filled with hot water at 40°C and cut using a pelletizer to obtain resin composition pellets. For tube molding, a circular die (outer diameter 15 mm, inner diameter 13.5 mm) was connected to a φ50 mm single-screw extruder and extrusion molding was performed. The cylinder temperature and die temperature were both set to 160°C, and the resin composition pellets were added and extruded into a tube. The extruded tube was passed through a 40°C water bath and taken up at 30 m / min to form a tube with an inner diameter of 5.6 mm and a thickness of 0.2 mm.

[0110] (Examples 2 to 6, Comparative Examples 1 to 4) Resin composition pellets and tubes were prepared in the same manner as in Example 1, except that the formulation was changed as shown in Table 1, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 1.

[0111] [Table 1]

[0112] The following can be seen from Table 1. Comparative Examples 1 and 2 have a relatively low weight-average molecular weight and a low content of copolymer (A) having a relatively low content of 3-hydroxybutyrate units, at less than 21% by weight. The 50% fracture energy measured at 5°C or 2°C is low, indicating insufficient impact resistance at low temperatures.

[0113] Comparative Examples 3 and 4 do not contain copolymer (B), which has a relatively high weight-average molecular weight. These examples also have low 50% breaking energy values ​​measured at 5°C or 2°C.

[0114] On the other hand, Examples 1 to 6 contain a predetermined amount of copolymer (A) and copolymer (B), and compared to Comparative Examples 1 to 4, the 50% fracture energy measured at 5°C or 2°C is higher, indicating that impact resistance at low temperatures has been improved.

Claims

1. A resin tube containing a poly(3-hydroxyalkanoate)-based resin component, The poly(3-hydroxyalkanoate) resin component is A copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units, having a weight average molecular weight of 400,000 or more and less than 700,000 and a content of 3-hydroxybutyrate units of 50 mol% or more and 76 mol% or less, and The copolymer (B) contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, and has a weight-average molecular weight of 700,000 or more. The resin tube has a content of copolymer (A) of 21% by weight or more and 40% by weight or less, and a content of copolymer (B) of 1% by weight or more and 20% by weight or less, based on the total amount of the poly(3-hydroxyalkanoate)-based resin component.

2. 2. The resin tube according to claim 1, wherein the copolymer (B) has a content of 3-hydroxybutyrate units of 50 mol % or more and 92 mol % or less.

3. the poly(3-hydroxyalkanoate)-based resin component further comprises poly(3-hydroxybutyrate) (C1) and / or a copolymer (C2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, which has a weight-average molecular weight of 100,000 or more and less than 700,000 and a content of 3-hydroxybutyrate units of 94 mol % or more and 99 mol % or less, The resin tube according to claim 1 or 2, wherein the total content of the poly(3-hydroxybutyrate) (C1) and the copolymer (C2) is 40% by weight or more of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

4. 4. The resin tube according to claim 3, wherein the content of poly(3-hydroxybutyrate) (C1) is 10% by weight or more of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

5. 3. The resin tube according to claim 1, wherein the content of the plasticizer (D) is 0 to 3 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxyalkanoate)-based resin component.

6. 3. The resin tube according to claim 1, wherein the wall thickness is 0.01 mm or more and 10 mm or less.

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